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The Patient > Endocrinology > Flashcards

Endocrinology Flashcards

1
Q

What types of hormones are there?

A
  • modified amino acids
  • peptides (3-20 amino acids)
  • proteins (single or mulitple subunits)
  • complex chemicals e.g. steroids
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2
Q

Examples of peptide hormones?

A

Oxytocin, anti-diuretic hormone

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3
Q

Similarities between oxytocin and ADH?

A

amino acid sequence differs at only two positions

can cause some cross over effects

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4
Q

Examples of protein hormones (single subunit)?

A

Growth hormone, prolactin

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5
Q

What does growth hormone do?

A

stimulates growth, cell division and regeneration. mitogen, specific to only certain cells

also known as somatotropin or somatropin

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6
Q

What does prolactin do?

A

properties and functions resembling both a hormone and a cytokine

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7
Q

Examples of protein hormones with multiple subunits?

A

TSH, FSH, insulin

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8
Q

How must protein hormones be administered clinically?

A

not orally as they get digested

  • IV or sc injection
  • inhaled
  • depot formulations
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9
Q

HOw is adrenaline synthesised from tyrosine?

A
  1. tyrosine hydroxylase adds OH and forms dihydroxyphenylalanine (L-DOPA)
  2. DOPA decarboxylase removes carboxylate to form dopamine
  3. Dopamine b-hydroxylase forms noradrenaline
  4. phenethanolamine N-methyltransferase forms adrenaline
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10
Q

How does the body produce adrenaline only in the adrenal glands?

A

Only adrenal glands express the enzymes to progress from dopamine, and contain large amounts of N-methyltransferase

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11
Q

What type of hormone is melatonin and how is it produced?

A

modified amino acid

comes from tryptophan, via serotonin

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12
Q

Typical base structure of steroids?

A

4 ring, C17 structure

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13
Q

What is a primary endocrine organ?

A

Primary function is secretion of hormones

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14
Q

What is a secondary endocrine organ?

A

Non-endocrine primary function, but do secrete hormones

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15
Q

Examples of primary endocrine glands?

A

Pineal, hypothalamus, Pituitary, thyroid, Adrenal, parathyroid, thymus, pancreas, testes

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16
Q

Examples of secondary endocrine glands?

A

Heart, stomach, liver, kidneys, small intestine, skin

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17
Q

Function of the thymus?

A

produces thymosin, which stimulates activity of T cells and antibody production in bone marrow

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18
Q

Where are the adrenal glands and what is their function?

A

at the top of the kidneys. mainly releasing hormones in response to stress

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19
Q

What is produced in the adrenal medulla?

A

Adrenaline and noradrenaline

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20
Q

What is produced in the adrenal cortex?

A

Corticosteroids

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21
Q

What is the HPA axis?

A

Hypothalamus: releases Corticotropin releasing hormone
A. Pituitary: releases Adrenocorticotropic hormone (ACTH)
Adrenal cortex: releases cortisol

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22
Q

Functions of the ovaries?

A

secrete steroids: progesterone and oestrogen
protein hormones: inhibin and relaxin

regulated by pituitary hormones FSH and LH

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23
Q

Primary functions of the testes?

A

spermatogenesis, producing steroid hormones (testosterone)

regulated by FSH and LH

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24
Q

Functions of the placenta?

A

facilitates nutrient uptake, removal of waste products & gas exchange via the maternal blood supply

produces steroid hormones (oestrogen and progesterone) and protein hormones (chorionic gonadotropin, corticotropin releasing hormone, placental lactogenic)

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25
Q

Endocrine functions of the heart?

A

Atrial natriuretic peptide (ANP) stimulates kidney to secrete more salt….. Thereby decreases excess blood volume, high BP and high blood sodium concentration

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26
Q

Endocrine functions of the GI tract?

A

Largest endocrine organ - over 30 hormones

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27
Q

Endocrine functions of the kidney?

A

Juxtaglomerular cells secrete renin (which indirectly signals adrenal cortex to produce aldosterone)

also release erythropoietin signals bone marrow to increase RBC production

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28
Q

What are the three regions of the adrenal cortex (outer first)?

A

Zona glomerulosa, Zona fasciculata, Zona reticularis

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29
Q

What hormones are produced in the zona glomerulosa?

A

Mineralocorticoids e.g. aldosterone

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30
Q

What hormones are produced in the zona fasciculata?

A

glucocorticoids e.g. cortisol

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31
Q

What hormones are produced in the zona reticularis?

A

Adrenal androgens

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32
Q

Key points regarding steroid synthesis?

A
  • steroids are not stored, they are synthesised on demand
  • synthesised from cholesterol
  • rate limiting step is first one, cholesterol to pregnenolone
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33
Q

What is the conversion of cholesterol to pregnenolone regulated by?

A

ACTH

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34
Q

Physiological actions of glucocorticoids?

A
  • metabolic effects
  • anti-inflammatory
  • immunosuppressive
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35
Q

Physiological actions of mineralorticoids?

A

water and electrolyte balance

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36
Q

Physiological actions of adrenal androgens?

A

maturation and development

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37
Q

What is transcortin?

A

corticosteroid binding globulin - carrier

binds 90% of cortisol and 60% of aldosterone

does not bind to synthetic steroids

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38
Q

What is albumin?

A

Another transport protein, binds both natural and synthetic steroids

39
Q

What can trigger the HPA axis pathway?

A

Stress

40
Q

Mechanism of action of mineralocorticoids?

A
  • receptors have limited tissue distribution
  • cause sodium reuptake and fluid resorption, leading to K loss
  • spironolactone is a competitie inhibitor of MC receptors
41
Q

Examples and half lives of short acting steroids?

A

hydrocortisone, fludrocortisone

8-12 hours

42
Q

Examples and half lives of intermediate acting steroids?

A

prednisolone 12-36 hours

43
Q

Examples and half lives of long acting steroids?

A

dexamethasone, betamethasone

36-72hours

44
Q

Which synthetic steroids have mixed glucocorticoid and mineralocorticoid activity?

A

prednisolone

45
Q

Which synthetic steroids have pure glucocorticoid activity?

A

dexamethasone, betamethasone, beclomethasone

46
Q

Which synthetic steroids have mainly mineralocorticoid activity?

A

fludrocortisone

47
Q

Place of steroids in addisons disease treatment?

A

replacement therapy for adrenal failure

Hydrocortisone (GC) with or without fludrocortisone (MC)
- limited side effects as mimin normal plasma concentrations

48
Q

What is congenital adrenal hyperplasia?

A
  • fault in steroidogenesis pathway
  • insufficient cortisol produced (and too many androgens) so no negative feedback on hypothalamus and pituitary
  • increased output of ACTH
49
Q

How is congenital adrenal hyperplasia treated?

A

synthetic cortisol to provide the negative feedback

limited side effects as normal plasma concentrations are mimicked

50
Q

Mechanism of steorids used for inflammation/immunosuppression?

A

Reduce mediators of inflammation and immune responses inc prostaglandin, cytokines, NO, IgG, etc

51
Q

Effects of excessive glucocoritcoid use?

A
  • drug induced Cushing’s
  • osteoporosis
  • increased risk of infection
52
Q

What is aminoglutethimide?

A

inhibits several enzymes in the steroidogenesis pathway

used for Cushing’s, post menopausal breast cancer, prostate cancer

53
Q

What is Metyrapone?

A

Inhibits 11 β-hydroxylase so reduces synthesis of gluco and mineralocorticoids - indirectly increases ACTH as less negative feedback

used for: testing A. pituitary function, Cushing’s, hyperaldosteronism
can cause manly hair growth in women due to excess androgens

54
Q

What is Synacthen?

A

synthetic peptide, ACTH analogue

  • stimulates synthesis and release of adrenal hormones
  • used to diagnose adrenal cortical insufficiency
55
Q

Location of the hypothalamus?

A

just below the thalamus above the brain stem

56
Q

Location of the pituitary gland?

A

in a small bony cavity below hypothalamus

57
Q

Why can pituitary tumour early signs be visual disturbances?

A

can only grow upwards due to bone, so meets optic nerve

58
Q

How does the hypothalamus link to the anterior pituitary?

A

parvicellular neurones - secrete regulatory hormones into the blood which travels down to AP (circulatory link)

59
Q

How does the hypothalamus link to the posterior pituitary?

A

Magnocellular neurones - long axons which release hormones directly into PP (direct neuro-endocrine link)

60
Q

Tropic effect of prolactin releasing hormone?

A

positive. causes AP to release prolactin, which acts on mammary development and lactation

hypothetical - hasn’t been proven to have an effect yet

61
Q

Tropic effect of prolactin inhibiting hormone?

A

negative. inhibits release of prolactin, which acts on mammary development and lactation

62
Q

Tropic effect of thyrotropin releasing hormone?

A

positive. stimulates release of TSH in AP, which causes release of thyronines in the thyroid

63
Q

Tropic effect of corticotropin releasing hormone?

A

positive. stimulates release of ACTH which acts on the adrenal cortex

64
Q

Tropic effect of growth hormone releasing hormone?

A

positive. stimulates release of growth hormone from AP which causes release of growth factors

65
Q

Tropic effect of growth hormone inhibiting hormone?

A

negative. inhibits release of growth hormone from AP

66
Q

Tropic effect of gonadotropin releasing hormone?

A

positive. stimulates release of FSH and LH from AP

67
Q

How to remember the anterior pituitary hormones?

A 
Flat Pig
FSH
LH
ACTH
TSH
Pi rolactin
Growth hormone

Flat are tropic, PiG are non tropic

68
Q

Where are the gonadotropins synthesised and stored?

A

gonadotropes

69
Q

Functions of gonadotropes?

A

FSH: ovaries to produce oestrogen
LH: ovulation and corpus luteum growth, plus androen secretion in testes

70
Q

What is corticotropin and where is it stored/synthesised?

A

ACTH - corticotropes

71
Q

What is thyrotropin and where is it stored/synthesised?

A

TSH - thyrotropes

72
Q

What is the HPT axis?

A

determines thyroxine secretion
short loop feedback: thyroid hormones stop TSH secretion
long loop feedback: thyroid hormones inhibit TRH secretion from hypothalamus

73
Q

What are the three feedback loops for CRH/ACTH?

A

ultra short: CRH inhibits further secretion of CRH

short: cortisol inhibits ACTH secretion
long: cortisol inhibits CRH secretion

74
Q

Structure and functions of prolactin?

A
  • 198 amino acid chain
  • synthesised/stored in lactotropes
  • effects on breast tissue for lactation
75
Q

Most common pituitary tumour and how is it treated?

A

prolactinoma: treated with dopamine receptor agonists eg. bromocriptine, cabergoline

76
Q

Structure and functions of growth hormone?

A
  • 191 amino acid protein

- synthesised/stored in somatotropes

77
Q

effects of hypersecretion of growth hormone?

A

gigantism in children, acromegaly in adults

78
Q

How is acromegaly treated?

A

Somatostatin (growth hormone inhibiting hormone)

79
Q

Mechanism of somatostatin?

A

regulates production of growth hormone, and affects cell proliferation/growth via somatostatin receptors

80
Q

Why is a synthetic analogue of somatostatin used for treatment?

A

longer half life (90 min vs 3)

only 8 amino acids instead of 14

81
Q

What causes growth hormone deficiency?

A
  • hypothalamic or pituitary tumour
  • GH gene mutation
  • head injury/infection
  • radiotherapy
  • GH resistance (Laron dwarfism) - mutations in the binding protein or receptor
82
Q

How is growth hormone deficiency treated?

A

somatotropin

7 preps available, made by recombinant DNA technology, identical to human sequence

83
Q

What is protirelin?

A

TRH - treatment for severe hypothyroidism (iv injection, rarely used)

84
Q

What is gonadorelin?

A

GnRH - induces FSH and LH. used for endometriosis and infertility

85
Q

What is vasopressin?

A

Treatment for pituitary diabetes insipidus

86
Q

What hormones are secreted by the posterior pituitary?

A

oxytocin and vasopressin

87
Q

Functions of oxytocin?

A
  • stimulation of milk ejection
  • stimulation of uterinevsmooth muscle contraction at birth
  • establishment of matternal behaviour
88
Q

What type of feedback loop controls oxytocin during childbirth?

A

Positive feedback - pressure on cervix causes release of oxytocin, which causes contraction and more pressure onthe cervix

89
Q

When must you stop synthetic oxytocin being used in labour?

A

contracts lasting >90 seconds, or <2 mins apart, fetal decelerations

monitor for blood pressure changes, hypertonicity of uterus and fetal heart rate

90
Q

Functions of vasopressin?

A
  • binds to receptors in the collecting ducts of the kidney
  • synthesis and insertion of aquaporins into kidney tubules
  • promotes reabsorption of water back into the kidenys
91
Q

What happens in the absence of vasopressin?

A

collecting ducts are virtually impermeable, all water flows out as urine

92
Q

What is diabetes insipidus?

A

lack of vaopressin response, leads to excessive urine production

93
Q

What are the two types of diabetes insipidus?

A
  • hypothalamic: insufficient vasopressin secretion. caused by trauma, infection or tumour affecting hypothalamus. treated with exogeneous vasopressin
  • nephrogenic: kidney is insensitive to vasopressin. caused by renal disease, receptor gene mutation or aquaporin gene mutation. treat by increasing water consumption
94
Q

What is the pineal gland?

A
  • 6mm, located in the epithalamus

- pinealocytes secrete melatonin, which regulates circadian rhythm. light inhibits production

The Patient (8 decks)

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